Depth finders or fish finders, as they are sometimes called, have become a common article of equipment for the sport fisherman. These devices have evolved from crude sonar repeaters which gave the user an indication of the bottom depth, to "flasher" units which used a circular dial to "flash" the depth of the bottom or of fish to the current generation of graphic LCD depth finders which utilize a Liquid Crystal Display to present a pictorial display of bottom structure and suspended fish. The current depth finders are sophisticated electronic devices; however, they are somewhat limited when the user changes the environment. Specifically, the current depth finders known to us are calibrated for use in fresh water or are calibrated for use in salt water or depict the depth in feet. However, none of the known devices are usable interchangably in salt or fresh water with a display in either feet or metric units. Accordingly, the sport fisherman who enjoys fresh and salt water fishing and who has the need or desire to correlate charts which may have depths printed in feet or meters thereon has heretofore been unable to obtain a single depth finder capable of functioning in the varied environments.